When the weather is dreary

Started Nov 24, 2019 | Discussions thread
Lasse Eisele
OP Lasse Eisele Senior Member • Posts: 2,009
Some random tips and thoughts on focus stacking

I started practicing focus stacking less than two months ago, so I’m really just a newbie myself. I have practiced almost every day since then and have made considerable progress through trial and error, but I still have lots to learn. Input from more experienced stackers are of course very welcome.

Why bother with focus stacking?
My goal is not to have everything in focus. I want my images to look reasonably natural, or at least believable. With focus stacking, you can get sufficient DOF on your main subject and still have a pleasing OOF background. This isn’t always easy to achieve. Anyway, I think everyone should ask themself what they are aiming for. Previsualisation is an important part of photography, in my opinion.

Start with in-camera stacking.
The in-camera stacking in my E-M1 and E-M1 II isn’t great (lots of stacking errors) but still very useful, especially if you’re handholding, since you get immediate feedback. If the camera reports ”stacking failed”, then you know you weren’t steady enough or the subject not still enough. When you feel comfortable with in-camera stacking, you can move on and turn it off. Just remember that the bracketing sequence is totally different when you turn it off, at least with Olympus. With stacking on, the camera brackets focus on either side of the point you focused on. With stacking off, the camera moves focus outwards, away from the camera, so you need to focus on the nearest part of the subject and then back off slightly. Sorry if I’m Olympus centric here. I don’t know how bracketing works on Panasonic bodies.

If you’re using in-camera stacking, then you’re limited to 8 shots with E-M1 and 15 shots with E-M1 II. Use the maximum number you can get. With stacking off, you get up to 999 images with either camera. I typically use around 40 shots for real macro photography (1:1 or thereabouts). For less extreme close-ups of flowers and such, you can get away with much less images.
The focus differential is a bit of a mystery, but I have found that 3 is a compromise that works most of the time.

Photoshop is much better than in-camera stacking, and Helicon Focus is better yet, though I think there is still room for improvement. I have also tried Zerene Stacker but didn’t like it much. Helicon Focus Pro lets you stack raw files and export the final stack as a DNG file. Very useful when you need it but I mostly use jpegs to save time.

Tripod or handheld?
A tripod is always a safer way to good stacking. The end result won’t necessarily be better but you’ll get more keepers. However, setting upp a tripod for ground level macro work is a nightmare, sometimes not even possible. You’ll probably have to reverse the center column and shoot with the camera upside down. And once you have managed to set it up, you find that the composition might be better with the camera 1 cm to the left. Or maybe to the right. One centimeter is a lot when you’re at 1:1. When you’re trying to adjust the tripod, you find that there is a rock or something else in the way. You realize that you would need a focus rail, preferably one that can be adjusted in four directions.
Does it sound like a hassle? It does to me, anyway. I often bring a tripod but almost never use it. I still recommend a tripod if you have the patience to use it.
Of course, I do what I can to hold the camera as still as possible. At 1:1, even a rather minor camera movement may ruin your stacking. The same goes for focus bracketing with long tele lenses, like the 300/4. Then I try to find support wherever I can, from a tree trunk, a rock or the ground itself (I’m very frequently lying down on the ground when I’m shooting so I always wear clothes that can take some mud).

Lily of the valley with berries. I could have used more shots here to cover the whole plant, but I'm pleased with the image as it is. Handheld with the 300/4, lying down on the ground.

Issues and difficulties
1. Wind. The subject needs to be absolutely still when you’re focus bracketing. The software can compensate for slight camera movement but it can’t handle a plant that is swaying in the wind. This is because the top of the plant moves more than the base, making it impossible to align the images.
While you’re waiting for that rare day with no wind at all, you can focus on subjects that don’t move easily. Or you can try to find places that are protected from the winds. There is generally much less wind at ground level than higher up. And even on a windy day there are often short moments that are totally still. All you need is patience.

Reindeer lichen with melting frost. You can see some intersecting detail here where I had do some retouching of soft halos. I also had to reduce the number of shots in the stack more than I had planned.

2. Halos from intersecting detail. This is the major problem with stacking, especially at very close distance. You see it as severe softening wherever there is detail behind other detail. The cause is, I believe, that the scale changes during the bracketing sequence, maybe from 1:1 to 1:1.2. This may result in parallax errors (just guessing here). None of the stacking programs I have tried have solved this issue, although Helicon Focus does it better than the others. Some clever AI would be needed here. The best way to deal with this issue is to make the image as clean as possible. Don’t include too many items and make sure that the background is well out of focus. It’s possible that a smaller focus differential would help too.
When you face the problem – you will! – you can try to minimize it by reducing the number of shots in the stack. Never use more shots than you really need.
3. Retouching. From the previous paragraph, it follows that retouching is often needed when you’re stacking macro shots (much less so at longer distances). Helicon Focus does include retouching tools, but I have found them difficult to use. I do almost all my retouching with the clone tool in Photoshop. Hopefully, there are similar tools in other editing apps.
4. Focus transitions. If you’re stacking images taken with a wide aperture, you’ll notice that focus transitions are very abrupt in areas that were not covered by the bracketing. This looks very unnatural, in my opinion. My advice is to avoid focus transitions as much as possible. Almost everything in your image should be either sharp or well out of focus. This is often best achieved by being level with the subject.

There you are. i hope that some of this was somewhat useful to some of you.


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